Multi-mode integrated starter-generator device with transmission assembly mounting arrangement

ABSTRACT

A combination starter-generator device is provided for a work vehicle having an engine. The starter-generator device includes an electric machine and a gear set configured to receive rotational input from the electric machine and the engine. The gear set includes a ring gear formed by a cylindrical base with a perimeter surface facing the engine and a circumferential row of castellations extending in a radial direction from the perimeter surface. The starter-generator device further includes a mounting arrangement comprising a drive plate configured to be secured to a crank shaft of the engine and a flex plate mounted to the drive plate. The flex plate includes a row of engagement apertures configured to receive the castellations of the ring gear to rotationally couple the ring gear to the engine via the mounting arrangement.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Not applicable.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE DISCLOSURE

This disclosure relates to work vehicle power systems, includingarrangements for starting mechanical power equipment and generatingelectric power therefrom.

BACKGROUND OF THE DISCLOSURE

Work vehicles, such as those used in the agriculture, construction andforestry industries, and other conventional vehicles may be powered byan internal combustion engine (e.g., a diesel engine), although it isbecoming more common for mixed power sources (e.g., engines and electricmotors) to be employed. In any case, engines remain the primary powersources of work vehicles and require mechanical input from a starter toinitiate rotation of the crankshaft and reciprocation of the pistonswithin the cylinders. Torque demands for starting an engine are high,particularly so for large diesel engines common in heavy-duty machines.

Work vehicles additionally include subsystems that require electricpower. To power these subsystems of the work vehicle, a portion of theengine power may be harnessed using an alternator or generator togenerate AC or DC power. The battery of the work vehicle is then chargedby inverting the current from the alternator. Conventionally, a belt,direct or serpentine, couples an output shaft of the engine to thealternator to generate the AC power. Torque demands for generatingcurrent from the running engine are significantly lower than for enginestart-up. In order to appropriately transfer power between the engineand battery to both start the engine and generate electric power, anumber of different components and devices are typically required,particularly with respect to mounting and coupling, thereby raisingissues with respect to size, cost, and complexity for operation,performance, and assembly.

SUMMARY OF THE DISCLOSURE

This disclosure provides a combined engine starter and electric powergenerator device with an integral transmission, such as may be used inwork vehicles for engine cold start and to generate electric power, thusserving the dual purposes of an engine starter and an alternator withmore robust power transmission to and from the engine in both cases.

In one aspect, the disclosure provides a combination starter-generatordevice for a work vehicle having an engine. The starter-generator deviceincludes an electric machine and a gear set configured to receiverotational input from the electric machine and from the engine and tocouple the electric machine and the engine in a first power flowdirection and a second power flow direction. The gear set is configuredto operate in one of at least a first gear ratio, a second gear ratio,or a third gear ratio in the first power flow direction and at least afourth gear ratio in the second power flow direction. The gear setincludes a ring gear formed by a cylindrical base with a perimetersurface facing the engine and a circumferential row of castellationsextending in a radial direction from the perimeter surface. Thestarter-generator device further includes a mounting arrangementcomprising a drive plate configured to be secured to a crank shaft ofthe engine and a flex plate mounted to the drive plate, wherein the flexplate includes a row of engagement apertures configured to receive thecastellations of the ring gear to rotationally couple the ring gear tothe engine via the mounting arrangement.

In another aspect, the disclosure provides a drivetrain assembly for awork vehicle. The drivetrain assembly includes an engine; an electricmachine; and a gear set configured to receive rotational input from theelectric machine and from the engine and to couple the electric machineand the engine in a first power flow direction and a second power flowdirection. The gear set is configured to operate in one of at least afirst gear ratio, a second gear ratio, or a third gear ratio in thefirst power flow direction and at least the third gear ratio in thesecond power flow direction. The gear set includes a ring gear formed bya cylindrical base with a perimeter surface facing the engine and acircumferential row of castellations extending in a radial directionfrom the perimeter surface. The drivetrain assembly further includes atleast one clutch selectively coupled to the gear set to effect thefirst, second, and third gear ratios in the first power flow directionand the fourth gear ratio in the second power flow direction; anactuation assembly configured to selectively shift the at least oneclutch from a disengaged position in which the at least one clutch isdecoupled from the gear set into an engaged position in which the atleast one clutch is coupled to the gear set; and a mounting arrangementcomprising a drive plate configured to be secured to a crank shaft ofthe engine and a flex plate mounted to the drive plate. The flex plateincludes a row of engagement apertures configured to receive thecastellations of the ring gear to rotationally couple the ring gear tothe engine via the mounting arrangement.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features and advantages willbecome apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of an example work vehicle in the formof an agricultural tractor in which the disclosed integratedstarter-generator device may be used;

FIG. 2 is a simplified partial isometric view of an engine of the workvehicle of FIG. 1 showing an example mounting location for an examplestarter-generator device;

FIG. 3 is a schematic diagram of a portion of a power transferarrangement of the work vehicle of FIG. 1 having an examplestarter-generator device;

FIG. 4 is a first isometric side view of a power transmission assemblyof the example starter-generator device that may be implemented in thework vehicle of FIG. 1;

FIG. 5 is an exploded isometric view of the power transmission assemblyof FIG. 4 for the example starter-generator device;

FIG. 6 is a partial isometric view of portions of a solenoid camactuation apparatus of the power transmission assembly of FIG. 5 for theexample starter-generator device;

FIG. 7 is an isometric view of the solenoid cam actuation apparatus andclutch arrangement removed from the power transmission assembly of FIG.4 for the example starter-generator device;

FIG. 8 is a cross-sectional view of the power transmission assembly ofFIG. 4 for the example starter-generator device;

FIG. 9 is a sectional cross-sectional view of the power transmissionassembly through line 9-9 of FIG. 8 for the example starter-generatordevice;

FIG. 10 is a partial isometric side view of a power transmissionassembly of the example starter-generator device that may be implementedin the work vehicle of FIG. 1;

FIG. 11 is an isometric view of a ring gear and a flex plate removedfrom the power transmission assembly of FIG. 4 for the examplestarter-generator device;

FIG. 12 is an exploded isometric view of the ring gear and the flexplate of FIG. 11 for the example starter-generator device;

FIG. 13 is an exploded isometric view of portions of a mountingarrangement removed from the power transmission assembly of FIG. 4 forthe example starter-generator device;

FIG. 14 is a partially exploded isometric view of portions of themounting arrangement removed from the power transmission assembly ofFIG. 4 for the example starter-generator device; and

FIG. 15 is an isometric view of portions of the mounting arrangementremoved from the power transmission assembly of FIG. 4 for the examplestarter-generator device.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The following describes one or more example embodiments of the disclosedstarter-generator device, as shown in the accompanying figures of thedrawings described briefly above. Various modifications to the exampleembodiments may be contemplated by one of skill in the art.

As used herein, unless otherwise limited or modified, lists withelements that are separated by conjunctive terms (e.g., “and”) and thatare also preceded by the phrase “one or more of” or “at least one of”indicate configurations or arrangements that potentially includeindividual elements of the list, or any combination thereof. Forexample, “at least one of A, B, and C” or “one or more of A, B, and C”indicates the possibilities of only A, only B, only C, or anycombination of two or more of A, B, and C (e.g., A and B; B and C; A andC; or A, B, and C).

As used herein, the term “axial” refers to a dimension that is generallyparallel to an axis of rotation, axis of symmetry, or centerline of acomponent or components. For example, in a cylinder or disc with acenterline and opposite, generally circular ends or faces, the “axial”dimension may refer to the dimension that generally extends in parallelto the centerline between the opposite ends or faces. In certaininstances, the term “axial” may be utilized with respect to componentsthat are not cylindrical (or otherwise radially symmetric). For example,the “axial” dimension for a rectangular housing containing a rotatingshaft may be viewed as a dimension that is generally in parallel withthe rotational axis of the shaft. Furthermore, the term “radially” asused herein may refer to a dimension or a relationship of componentswith respect to a line extending outward from a shared centerline, axis,or similar reference, for example in a plane of a cylinder or disc thatis perpendicular to the centerline or axis. In certain instances,components may be viewed as “radially” aligned even though one or bothof the components may not be cylindrical (or otherwise radiallysymmetric). Furthermore, the terms “axial” and “radial” (and anyderivatives) may encompass directional relationships that are other thanprecisely aligned with (e.g., oblique to) the true axial and radialdimensions, provided the relationship is predominately in the respectivenominal axial or radial dimension. Additionally, the term“circumferential” may refer to a collective tangential dimension that isperpendicular to the radial and axial dimensions about an axis.

Many conventional vehicle power systems include an internal combustionengine and/or one or more batteries (or other chemical power source)that power various components and subsystems of the vehicle. In certainelectric vehicles, a bank of batteries powers the entire vehicleincluding the drive wheels to impart motion to the vehicle. In hybridgas and electric vehicles, the motive force may alternate between engineand electric motor power, or the engine power may be supplemented byelectric motor power. In still other conventional vehicles, the electricpower system is used to initiate engine start up and to run thenon-drive electric systems of the vehicle. In the latter case, thevehicle typically has a starter motor that is powered by the vehiclebattery to turn the engine crankshaft to move the pistons within thecylinders. In further scenarios, the electric power system may provide aboost to an operating engine.

Some engines (e.g., diesel engines) initiate combustion by compressionof the fuel, while other engines rely on a spark generator (e.g., sparkplug), which is powered by the battery. Once the engine is operating ata sufficient speed, the power system may harvest the engine power topower the electric system as well as to charge the battery. Typically,this power harvesting is performed with an alternator or other type ofpower generator. The alternator converts alternating current (AC) powerto direct current (DC) power usable by the battery and vehicle electriccomponents by passing the AC power through an inverter (e.g., dioderectifier). Conventional alternators harness power from the engine bycoupling a rotor of the alternator to an output shaft of the engine (ora component coupled thereto). Historically this was accomplished by theuse of a dedicated belt, but in some more modern vehicles the alternatoris one of several devices that are coupled to (and thus powered by) theengine via a single “serpentine” belt.

In certain applications, such as in certain heavy-duty machinery andwork vehicles, it may be disadvantageous to have a conventional set-upwith separate starter and generator components. Such separate componentsrequire separate housings, which may require separate sealing orshielding from the work environment and/or occupy separate positionswithin the limited space of the engine compartment. Other enginecompartment layout complexities may arise as well.

The following describes one or more example implementations of animproved vehicle power system that addresses one or more of these (orother) matters with conventional systems. In one aspect, the disclosedsystem includes a combination or integrated device that performs theengine cranking function of a starter motor and the electric powergenerating function of a generator. The device is referred to herein asan integrated starter-generator device (“ISG” or “starter-generator”).This terminology is used herein, at least in some implementations of thesystem, to be agnostic to the type of power (i.e., AC or DC current)generated by the device. In some implementations, the starter-generatordevice may function to generate electricity in a manner of what personsof skill in the art may consider a “generator” device that produces DCcurrent directly. However, as used herein, the term “generator” shallmean producing electric power of static or alternating polarity (i.e.,AC or DC). Thus, in a special case of the starter-generator device, theelectric power generating functionality is akin to that of aconventional alternator, and it generates AC power that is subsequentlyrectified to DC power, either internally or externally to thestarter-generator device.

Further, in certain embodiments, the starter-generator device may have apower transmission assembly that automatically and/or selectively shiftsgear ratios (i.e., shifts between power flow paths having different gearratios). By way of example, the transmission assembly may include one ormore passive or active engagement components that engage or disengage toeffect power transmission through a power flow path. In this manner,bi-directional or other clutch (or other) configurations may be employedto carry out the cranking and generating functions with the appropriatecontrol hardware. As a result of the bi-directional nature of the powertransmission assembly, the power transfer belt arrangement may beimplemented with only a single belt tensioner, thereby providing arelatively compact and simple assembly. In addition to providing torquein two different power flow directions, the gear set may also beconfigured and arranged to provide power transmission from the electricmachine to the engine at one of two different speeds, e.g., according todifferent gear ratios. The selection of speed may provide additionalfunctionality and flexibility for the power transmission assembly.

In certain embodiments, the starter-generator device may include amounting arrangement with a direct mechanical power coupling to theengine that avoids the use of belts between the engine and thestarter-generator device. For example, the starter-generator device mayinclude within its housing a power transmission assembly with a gear setthat directly couples to an output shaft of the engine. The gear set maytake any of various forms including arrangements with enmeshing spur orother gears as well as arrangements with one or more planetary gearsets. Large gear reduction ratios may be achieved by the transmissionassembly such that a single electric machine (i.e., motor or generator)may be used and operated at suitable speeds for one or more types ofengine start up, as well as electric power generation. The mountingarrangement may include a torsional damper and flex plate to reducenoise and vibrations. The direct power coupling of the mountingarrangement between the starter-generator device and engine may increasesystem reliability, cold starting performance, and electric powergeneration of the system.

Some examples of the actuation assembly described below may useelectromechanical solenoid devices. As used herein with respect to thesolenoid devices, the term “activated” or “engaged” refers to a commandthat results in the associated clutch moving into the engaged position.In one example, the engage command for the solenoid devices results inthe respective armature being pushed out of the solenoid device, whichmay occur from applying a current to the coil within the solenoid topush the armature out of the solenoid or from discontinuing current tothe coil such that a spring pushes the armature out of the solenoid, orvice versa. In other examples, depending on configuration of the linkageand/or position of the solenoid assembly, the engage command for asolenoid device may result in the armature moving into the solenoiddevice in order to engage (or disengage) the associated clutch.

Various implementations will be discussed in greater detail below.

Referring to the drawings, an example work vehicle power system as adrivetrain assembly will be described in detail. As will become apparentfrom the discussion herein, the disclosed system may be usedadvantageously in a variety of settings and with a variety of machinery.For example, referring now to FIG. 1, the power system (or drivetrainassembly) 110 may be included in a work vehicle 100, which is depictedas an agricultural tractor. It will be understood, however, that otherconfigurations may be possible, including configurations with workvehicle 100 as a different kind of tractor, or as a work vehicle usedfor other aspects of the agriculture industry or for the constructionand forestry industries (e.g., a harvester, a log skidder, a motorgrader, and so on). It will further be understood that aspects of thepower system 110 may also be used in non-work vehicles and non-vehicleapplications (e.g., fixed-location installations).

Briefly, the work vehicle 100 has a main frame or chassis 102 supportedby ground-engaging wheels 104, at least the front wheels of which aresteerable. The chassis 102 supports the power system (or plant) 110 andan operator cabin 108 in which operator interface and controls (e.g.,various joysticks, switches levers, buttons, touchscreens, keyboards,speakers and microphones associated with a speech recognition system)are provided.

As schematically shown, the power system 110 includes an engine 120, anintegrated starter-generator device 130, a battery 140, and a controller150. The engine 120 may be an internal combustion engine or othersuitable power source that is suitably coupled to propel the workvehicle 100 via the wheels 104, either autonomously or based on commandsfrom an operator. The battery 140 may represent any one or more suitableenergy storage devices that may be used to provide electric power tovarious systems of the work vehicle 100.

The starter-generator device 130 couples the engine 120 to the battery140 such that the engine 120 and battery 140 may selectively interact inat least four modes. In a first (or cold engine start) mode, thestarter-generator device 130 converts electric power from the battery140 into mechanical power to drive the engine 120 at a first gear ratiocorresponding to a relatively high speed, e.g., during a relatively coldengine start up. In a second (or warm engine start) mode, thestarter-generator device 130 converts electric power from the battery140 into mechanical power to drive the engine 120 at a second gear ratiocorresponding to a relatively low speed, e.g., during a relatively warmengine start up. In a third (or boost) mode, the starter-generatordevice 130 converts electric power from the battery 140 into mechanicalpower at a third gear ratio corresponding to a relatively low speed todrive the engine 120 for an engine boost. In a fourth (or generation)mode, the starter-generator device 130 converts mechanical power at afourth (or the third) gear ratio from the engine 120 into electric powerto charge the battery 140. Additional details regarding operation of thestarter-generator device 130 during the engine start modes, the boostmode, and the generation mode are provided below.

As introduced above, the controller 150 may be considered part of thepower system 110 to control various aspects of the work vehicle 100,particularly characteristics of the power system 110. The controller 150may be a work vehicle electronic controller unit (ECU) or a dedicatedcontroller. In some embodiments, the controller 150 may be configured toreceive input commands and to interface with an operator via ahuman-machine interface or operator interface (not shown) and fromvarious sensors, units, and systems onboard or remote from the workvehicle 100; and in response, the controller 150 generates one or moretypes of commands for implementation by the power system 110 and/orvarious systems of work vehicle 100. In one example and as discussed ingreater detail below, the controller 150 may command current toelectromagnets associated with an actuator assembly to engage and/ordisengage the clutches within the starter-generator device 130. Othermechanisms for controlling such clutches may also be provided.

Generally, the controller 150 may be configured as computing deviceswith associated processor devices and memory architectures, ashydraulic, electrical or electro-hydraulic controllers, or otherwise. Assuch, the controller 150 may be configured to execute variouscomputational and control functionality with respect to the power system110 (and other machinery). The controller 150 may be in electronic,hydraulic, or other communication with various other systems or devicesof the work vehicle 100. For example, the controller 150 may be inelectronic or hydraulic communication with various actuators, sensors,and other devices within (or outside of) the work vehicle 100, includingvarious devices associated with the power system 110. Generally, thecontroller 150 generates the command signals based on operator input,operational conditions, and routines and/or schedules stored in thememory. For example, the operator may provide inputs to the controller150 via an operator input device that dictates the appropriate mode, orthat at least partially defines the operating conditions in which theappropriate mode is selected by the controller 150. In some examples,the controller 150 may additionally or alternatively operateautonomously without input from a human operator. The controller 150 maycommunicate with other systems or devices (including other controllers)in various known ways, including via a CAN bus (not shown), via wirelessor hydraulic communication means, or otherwise.

Additionally, power system 110 and/or work vehicle 100 may include ahydraulic system 152 with one or more electro-hydraulic control valves(e.g., solenoid valves) that facilitate hydraulic control of variousvehicle systems, particularly aspects of the starter-generator device130. The hydraulic system 152 may further include various pumps, lines,hoses, conduits, tanks, and the like. The hydraulic system 152 may beelectrically activated and controlled according to signals from thecontroller 150. The hydraulic system 152 may be omitted.

In one example, the starter-generator device 130 includes a powertransmission assembly (or transmission) 132, an electric machine ormotor 134, and an inverter/rectifier device 136, each of which may beoperated according to command signals from the controller 150. The powertransmission assembly 132 enables the starter-generator device 130 tointerface with the engine 120, particularly via a crank shaft 122 orother power transfer element of the engine 120, such as an auxiliarydrive shaft. The power transmission assembly 132 may include one or moregear sets in various configurations to provide suitable power flows andgear reductions, as described below. The power transmission assembly 132variably interfaces with the electric machine 134 in two different powerflow directions such that the electric machine 134 operates as a motorduring the engine start and boost modes and as a generator during thegeneration mode. In one example, discussed below, the power transmissionassembly 132 is coupled to the electric machine 134 via a power transferbelt arrangement. This arrangement, along with the multiple gear ratiosprovided by the power transmission assembly 132, permits the electricmachine 134 to operate within optimal speed and torque ranges in bothpower flow directions. The inverter/rectifier device 136 enables thestarter-generator device 130 to interface with the battery 140, such asvia direct hardwiring or a vehicle power bus 142. In one example, theinverter/rectifier device 136 inverts DC power from the battery 140 intoAC power during the engine start modes and rectifies AC power to DCpower in the generation mode. In some embodiments, theinverter/rectifier device 136 may be a separate component instead ofbeing incorporated into the starter-generator device 130. Although notshown, the power system 110 may also include a suitable voltageregulator, either incorporated into the starter-generator device 130 oras a separate component.

Reference is briefly made to FIG. 2, which depicts a simplified partialisometric view of an example mounting location of the starter-generatordevice 130 relative to the engine 120. In this example, the integratedstarter-generator device 130 mounts directly and compactly to the engine120 so as not to project significantly from the engine 120 (and therebyenlarge the engine compartment space envelope) or interfere with variousplumbing lines and access points (e.g., oil tubes and fill opening andthe like). Notably, the starter-generator device 130 may generally bemounted on or near the engine 120 in a location suitable for coupling toan engine power transfer element (e.g., a crank shaft 122 as introducedin FIG. 1).

Reference is additionally made to FIG. 3, which is a simplifiedschematic diagram of a power transfer belt arrangement 200 between thepower transmission assembly 132 and electric machine 134 of thestarter-generator device 130. It should be noted that FIGS. 2 and 3depict one example physical integration or layout configuration of thestarter-generator device 130. Other arrangements may be provided,including a more detailed implementation described below with referenceto FIGS. 4-15.

In FIG. 3, the power transmission assembly 132 is mounted to the engine120 and may be supported by a reaction plate 124. As shown, the powertransmission assembly 132 includes a first power transfer element 133that is rotatably coupled to a suitable drive element of the engine 120and a second power transfer element 135 in the form of a shaft extendingon an opposite side of the power transmission assembly 132 from thefirst power transfer element 133. Similarly, the electric machine 134 ismounted on the engine 120 and includes a further power transfer element137.

The power transfer belt arrangement 200 includes a first pulley 210arranged on the second power transfer element 135 of the powertransmission assembly 132, a second pulley 220 arranged on the powertransfer element 137 of the electric machine 134, and a belt 230 thatrotatably couples the first pulley 210 to the second pulley 220 forcollective rotation. As described in greater detail below, during theengine start modes, the electric machine 134 pulls the belt 230 torotate pullies 210, 220 in a first clock direction D1 to drive the powertransmission assembly 132 (and thus the engine 120); during the boostmode, the electric machine 134 pulls the belt 230 to rotate pullies 210,220 in a second clock direction D2 to drive the power transmissionassembly 132 (and thus the engine 120); and during the generation mode,the power transmission assembly 132 enables the engine 120 to pull thebelt 230 and rotate pullies 210, 220 in the second clock direction D2 todrive the electric machine 134.

As a result of the bi-directional configuration, the power transfer beltarrangement 200 may include only a single belt tensioner 240 to applytension to a single side of the belt 230 in both directions D1, D2.Using a single belt tensioner 240 to tension the belt 230 isadvantageous in that it reduces parts and complexity in comparison to adesign that requires multiple belt tensioners. As described below, thebi-directional configuration and associated simplified power transferbelt arrangement 200 are enabled by the bi-directional nature of thegear set in the power transmission assembly 132. Additionally, adifference in the circumferences of the first and second pullies 210,220 provides a change in the gear ratio between the power transmissionassembly 132 and the electric machine 134. In one example, the powertransfer belt arrangement 200 may provide a gear ratio of between3:1-5:1, particularly a 4:1 ratio.

Reference is now made to FIG. 4, which is a more detailed isometric sideview of the power transmission assembly 132 of the examplestarter-generator device, and FIG. 5, which is an exploded view of thepower transmission assembly 132 of FIG. 4. In one example, the powertransmission assembly 132 includes a gear set 320, a clutch arrangement350 (obscured in FIGS. 4 and 5), and a cam actuation apparatus 390supported by a primary housing 302 and mounting arrangement 305 thatprovides a direct mechanical coupling between the power transmissionassembly 132 and the engine 120 (FIG. 3). As one example describedbelow, the gear set 320 operates to transfer torque between the engine120 and electric machine 134 at predetermined gear ratios that areselected based on the status of the clutch arrangement 350, which iscontrolled by the cam actuation apparatus 390 based on signals from thecontroller 150. Each aspect of an example power transmission assembly132 will be discussed below.

The primary housing 302 of the power transmission assembly 132 includesa stationary housing portion 303 that supports a housing cover 304 andthe mounting arrangement 305. In one example, the mounting arrangement305 is formed by one or more leg members 306 that extend from thestationary housing portion 303 and function to mount the powertransmission assembly 132 to the engine 120 (FIG. 1). Generally, thestationary housing portion 303 and housing cover 304 are configured tosupport, shield, and/or protect other portions of the power transmissionassembly 132. As shown, the housing cover 304 includes an aperture 307that enables the power transfer element 135 in the form of pulley 210(e.g., as discussed above with reference to FIG. 3) to be rotationallycoupled to an input shaft 310 of the power transfer assembly 132, whichin turn is coupled to the gear set 320 of the power transfer assembly132. In one example, the pulley 210 may be rotationally coupled to theinput shaft 310 with a fastener 308 through the aperture 307 of thehousing cover 304.

On one end of the power transmission assembly 132, mounting arrangement305 may be considered to include a drive plate 309 coupled to the gearset 320 as a power transfer element (e.g., element 133 of FIG. 3).Generally, the drive plate 309 facilitates coupling the powertransmission assembly 132 to the engine 120 (FIG. 3). In one example,the drive plate 309 is coupled to the engine crank shaft. The driveplate 309 may also operate as a torsional damper in order to dampenvibrations at the crankshaft of the engine 120 (FIG. 3), as discussed ingreater detail below.

Reference is now made to FIG. 6, which is a partial isometric view ofportions of the power transmission assembly 132 with the primary housing302 removed to more clearly depict the solenoid cam actuation apparatus390. It should be noted that the cam actuation apparatus 390 is just oneexample, and other arrangements may be provided. Generally, the camactuation apparatus 390 includes a base or reaction member 392 formed asa ring or plate-like structure with a first face 393, second face 394,outer perimeter 395, and inner perimeter 396. The inner perimeter 396defines an opening 397 to accommodate the connection between the inputshaft 310 and the power transfer element 135. The opening 397 in thereaction member 392 also accommodates the connections between the camactuation apparatus 390 and the clutch arrangement 350, as discussedbelow.

The reaction member 392 additionally supports a number of solenoiddevices 410, 430, 450, 470, 490, 510, 530 that interact with the clutcharrangement 350 (obscured in FIG. 6). Specifically, the reaction member392 supports the solenoid devices 410, 430, 450, 470, 490, 510, 530 onflanges 411, 431, 451, 471, 491, 511, 531. As described in greaterdetail below, the cam actuation apparatus 390 includes one or more first(or low) solenoid devices 410, 430; one or more second (or mid) solenoiddevices 450, 470; and one or more third (or high) solenoid devices 490,510, 530. In the depicted example, the cam actuation apparatus 390includes two low clutch solenoid devices 410, 430, two mid clutchsolenoid devices 450, 470, and three high clutch solenoid devices 490,510, 530, although other examples may have different numbers of solenoidapparatuses.

Each of the solenoid devices 410, 430, 450, 470, 490, 510, 530 iscoupled to the clutch arrangement 350 via a linkage assembly 412, 432,452, 472, 492, 512, 532 that includes a link member and pivot member.Specifically, each linkage assembly 412, 432, 452, 472, 492, 512, 532extends between the respective solenoid device 410, 430, 450, 470, 490,510, 530 and an actuation pin 416, 436, 456, 476, 496, 516, 536. Asdescribed below, the actuation pins 416, 436, 456, 476, 496, 516, 536are axially repositionable within the clutch arrangement 350 to axiallymove portions of the clutch arrangement 350 between engaged anddisengaged positions to modify the power transfer characteristics of thegear set 320. The actuation pins 416, 436, 456, 476, 496, 516, 536 maybe supported by a stationary spindle or hub 351 that circumscribes theinput shaft 310.

The reaction member 392, solenoid devices 410, 430, 450, 470, 490, 510,530, and clutch arrangement 350 are described in more detail withreference to FIG. 8, which is an isometric view of these elementsremoved from the power transmission assembly 132. The view of FIG. 8depicts a complete set of the solenoid devices 410, 430, 450, 470, 490,510, 530 and clutch arrangement 350. The clutches 360, 370, 380 may beconsidered “shifting” or “dog” clutches that are actively actuated tomodify power flow within the power transmission assembly 132.

As an example, FIG. 8 depicts the solenoid devices 410, 430 mounted onthe reaction member 392 and coupled to the actuation pins 416, 436 vialinkage assemblies 412, 432 to actuate a low clutch 360 of the clutcharrangement 350. As described in greater detail below, the low clutch360 is repositionable between an engaged position and a disengagedposition relative to the gear set 320 in order to modify the powertransfer through the gear set 320. In one example, the low clutch 360 isparticularly engaged during a cold engine start mode to enable theelectric machine 134 to drive the engine 120 at a first power ratio.

In this example, the solenoid devices 410, 430 associated with the lowclutch 360 are mounted to the undersides (or engine-sides) of theflanges 411, 431 on the outer perimeter 395 of the reaction member 392.The solenoid devices 410, 430 may be secured to the flanges 411, 431 inany suitable manner, such as by screws or other fasteners.

As introduced above, the solenoid devices 410, 430 are electromechanicalactuators that generate linear movement at a respective armature bymanipulating an induced magnetic field within the solenoid devices 410,430. As the solenoid devices 410, 430 are activated or engaged, thearmatures move out of the solenoid devices 410, 430. The solenoiddevices 410, 430 are relatively low profile devices that enable asmaller overall package. Although two solenoid devices 410, 430 areprovided in the depicted example, other embodiments may only have asingle solenoid device or more than two solenoid devices.

The link members of the linkage assemblies 412, 432 extend between thearmatures of the solenoid devices 410, 430 and the actuation pins 416,436 and are pivotable about pivot members on the reaction member 392. Asa result of the armatures moving out of the solenoid devices 410, 430,the link members are pivoted to move the low clutch 360 in the oppositeaxial direction, e.g., into the gear set 320. The arrangement of thelinkage assemblies 412, 432 enables the solenoid devices 410, 430 to useleverage with the reaction member 392 to facilitate operation in a morecompact and efficient manner, for example, by enabling advantageous useof beneficial lever ratios as a function of travel and force.

The solenoid devices 410, 430 associated with the low clutch 360 mayinclude at least one connection element that enables commands and/orpower between the respective solenoid devices 410, 430, the controller150 (FIG. 1), and/or other sources. The connection elements may be wiredor wireless connections. Positioning the solenoid devices 410, 430around the outer perimeter 395 of the reaction member 392 may facilitatewire routing, if applicable, between the controller 150 and theconnection elements.

The low clutch 360 is generally ring shaped with an inner perimeter thatmay be splined to facilitate mounting the low clutch 360 (e.g., on thespindle 351 or another element within or proximate to the gear set 320).A set of tabs may be positioned on the inner perimeter and define pinmounting holes that receive the actuation pins 416, 436. In particular,the pins 416, 436 are secured to the low clutch 360 at the tabs suchthat axial movement of the pins 416, 436 by the solenoid devices 410,430 functions to axially reposition the low clutch 360. As discussed ingreater detail below, the low clutch 360 additionally includes one ormore teeth to engage elements of the gear set 320.

As a further example, solenoid devices 450, 470 may be mounted on thereaction member 392 and coupled to the actuation pins 456, 476 vialinkage assemblies 452, 472 to actuate a mid clutch 370 of the clutcharrangement 350. As described in greater detail below, the mid clutch370 is repositionable between an engaged position and a disengagedposition relative to the gear set 320 in order to modify the powertransfer through the gear set 320. In one example, the mid clutch 370 isparticularly engaged during a warm engine start mode to enable theelectric machine 134 to drive the engine 120 at a second power ratio.

In this example, the solenoid devices 450, 470 associated with the midclutch 370 are mounted to the undersides (or engine-sides) of theflanges 451, 471 on the outer perimeter 395 of the reaction member 392.The solenoid devices 450, 470 may be secured to the flanges 451, 471 inany suitable manner, such as by screws or other fasteners.

As introduced above, the solenoid devices 450, 470 associated with themid clutch 370 are electromechanical actuators that generate linearmovement at a respective armature by manipulating an induced magneticfield within the solenoid devices 450, 470. As the solenoid devices 450,470 are activated or engaged, the armatures move out of the solenoiddevices 410, 430. The solenoid devices 450, 470 are relatively lowprofile devices that enable a smaller overall package. Although twosolenoid devices 450, 470 are provided in the depicted example, otherembodiments may only have a single solenoid device or more than twosolenoid devices.

The link members of the linkage assemblies 452, 472 extend between thearmatures of the solenoid devices 450, 470 and the actuation pins 456,476 and are pivotable about pivot members on the reaction member 392. Asa result of the armatures moving out of the solenoid devices 450, 470,the link members are pivoted to move the mid clutch 370 in the oppositeaxial direction, e.g., into the gear set 320. The arrangement of thelinkage assemblies 452, 472 enables the solenoid devices 450, 470 to useleverage with the reaction member 392 to facilitate operation in a morecompact and efficient manner, for example, by enabling advantageous useof beneficial lever ratios as a function of travel and force.

The solenoid devices 450, 470 may include at least one connectionelement that enables commands and/or power between the respectivesolenoid devices 450, 470, the controller 150 (FIG. 1), and/or othersources. The connection elements may be wired or wireless connections.Positioning the solenoid devices 450, 470 around the outer perimeter 395of the reaction member 392 may facilitate wire routing, if applicable,between the controller 150 and the connection elements.

The mid clutch 370 is generally ring shaped having an outer perimeterthat may be splined to facilitate mounting the mid clutch 370 (e.g., onthe spindle 351 or another element within or proximate to the gear set320). A set of tabs is positioned on the outer perimeter and define pinmounting holes that receive the actuation pins 436, 456. In particular,the pins 436, 456 are secured to the mid clutch 370 at the tabs suchthat axial movement of the pins 436, 456 by the solenoid devices 450,470 functions to axially reposition the mid clutch 370. As discussed ingreater detail below, the mid clutch 370 additionally includes one ormore teeth extending from the first face to engage elements of the gearset 320. Additional details regarding the mid clutch 370, particularlyregarding the engagement of the mid clutch 370 with the gear set 320,are provided below. The low clutch 360 and mid clutch 370 are sized suchthat the mid clutch 370 may be concentrically arranged within the lowclutch 360. Other arrangements may be provided.

As a further example, solenoid devices 490, 510, 530 may be mounted onthe reaction member 392 and coupled to the actuation pins 496, 516, 536via linkage assemblies 492, 512, 532 to actuate a high clutch 380 of theclutch arrangement 350. As described in greater detail below, the highclutch 380 is repositionable between an engaged position and adisengaged position relative to the gear set 320 in order to modify thepower transfer through the gear set 320. In one example, the high clutch380 is particularly engaged during a boost mode to enable the electricmachine 134 to drive the engine 120 at a third power ratio or during ageneration mode to enable the engine 120 to drive the electric machine134 at the third power ratio.

In this example, the solenoid devices 490, 510, 530 associated with thehigh clutch 380 are mounted to the electric machine-side of the flanges491, 511, 531 on the outer perimeter 395 of the reaction member 392. Thesolenoid devices 490, 510, 530 may be secured to the flanges 491, 511,531 in any suitable manner, such as by screws or other fasteners.

As introduced above, the solenoid devices 490, 510, 530 associated withthe high clutch 380 are electromechanical actuators that generate linearmovement at a respective armature by manipulating an induced magneticfield within the solenoid devices 490, 510, 530. As the solenoid devices490, 510, 530 are engaged, the armatures move into the solenoid devices490, 510, 530 to engage the high clutch 380. In one example, thesolenoid devices 490, 510, 530 may be energized during disengagement andde-energized during engagement, although arrangements may vary. Thesolenoid devices 490, 510, 530 are relatively low profile devices thatenable a smaller overall package. Although three solenoid devices 490,510, 530 are provided in the depicted example, other embodiments mayonly have fewer solenoid devices (e.g., one or two) or more than threesolenoid devices.

The link members of the linkage assemblies 492, 512, 532 extend betweenthe armatures of the solenoid devices 490, 510, 530 and the actuationpins 496, 516, 536 and are pivotable about pivot members on the reactionmember 392. As a result of the armatures moving out of the solenoiddevices 490, 510, 530, the link members are pivoted to move the highclutch 380 in the opposite axial direction, e.g., towards the gear set320. The arrangement of the linkage assemblies 492, 512, 532 enables thesolenoid devices 490, 510, 530 to use leverage with the reaction member392 to facilitate operation in a more compact and efficient manner, forexample, by enabling advantageous use of beneficial lever ratios as afunction of travel and force.

Additionally, the solenoid devices 490, 510, 530 associated with thehigh clutch 380 include at least one connection element that enablescommands and/or power between the respective solenoid devices 490, 510,530, the controller 150 (FIG. 1), and/or other sources. The connectionelements may be wired or wireless connections. Positioning the solenoiddevices 490, 510, 530 around the outer perimeter 395 of the reactionmember 392 may facilitate wire routing, if applicable, between thecontroller 150 and the connection elements.

The high clutch 380 is generally ring shaped with a first (or electricmachine-side) face, a second (or engine-side) face, an inner perimeter,and an outer perimeter. A set of tabs is positioned on the outerperimeter and define pin mounting holes that receive the actuation pins496, 516, 536. In particular, the pins 496, 516, 536 are secured to thehigh clutch 380 at the tabs such that axial movement of the pins 496,516, 536 by the solenoid devices 490, 510, 530 functions to axiallyreposition the high clutch 380. Although not shown in FIG. 9, the highclutch 380 may be secured into position and/or mounted on a sleeve,support element, and/or sliding hub. Additional details regarding thehigh clutch 380, particularly regarding the engagement of the highclutch 380 with the gear set 320, are provided below.

The operation of the gear set 320, clutch arrangement 350, and camactuation apparatus 390 will now be described with reference to FIG. 8,which is cross-sectional views of the power transmission assembly 132.As introduced above, the gear set 320 of the power transmission assembly132 is configured to transfer power between the pulley 210 and the driveplate 309. The gear set 320 is generally housed within an annular gearhousing 311, portions of which, in this example, rotate with aspects ofthe gear set 320. Bearings 312 may be provided within the gear housing311 to enable rotation of certain elements relative to stationaryportions.

In the view of FIG. 8, a first side of the power transmission assembly132 is oriented towards the electric machine 134, and a second side ofthe power transmission assembly 132 is oriented towards the engine 120.As noted above, the input shaft 310 may be directly connected to thepower transfer element 135 with a fastener or bolt 308 or othermechanism; and in further examples, the input shaft 310 may be coupledthrough intermediate components, such as a flange or boss. It should benoted that, although the shaft 310 is described as an “input” shaft, itmay transfer power both into and out of the power transmission assembly132, depending on the mode, as described below. The input shaft 310generally extends through the power transmission assembly 132 to definea primary axis of rotation 300.

The gear set 320 of the power transmission assembly 132, in thisexample, is a two-stage planetary gear set that enables the powertransmission assembly 132 to interface with the electric machine 134(e.g., via the power transfer belt arrangement 200) and the engine 120(e.g., via coupling to the crank shaft 122 of the engine 120, asdescribed in greater detail below). In some embodiments, the input shaft310 may be considered part of the planetary gear set 320. Although oneexample configuration of the planetary gear set 320 is described below,other embodiments may have different configurations.

The planetary gear set 320 includes a first-stage sun gear 322 mountedfor rotation on the input shaft 310. The first-stage sun gear 322includes a plurality of teeth or splines that mesh with a set offirst-stage planet gears 324 that circumscribe the first-stage sun gear322. In one example, the first-stage planet gears 324 include a singlecircumferential row of one or more planet gears, although otherembodiments may include radially stacked rows, each with an odd numberof planet gears in the radial direction.

The first-stage planet gears 324 are supported by a first-stage planetcarrier 326, which circumscribes the first-stage sun gear 322, as wellas the input shaft 310, and is at least partially formed by first andsecond radially extending, axially facing carrier plates. Thefirst-stage carrier plates of the first-stage planet carrier 326 includea row of mounting locations for receiving axles extending through andsupporting the first-stage planet gears 324 for rotation. As such, inthis arrangement, each of the planet axles respectively forms anindividual axis of rotation for each of the first-stage planet gears324, and the first-stage planet carrier 326 enables the set offirst-stage planet gears 324 to collectively rotate about thefirst-stage sun gear 322.

The gear set 320 further includes a ring gear 332 that circumscribes thefirst-stage sun gear 322 and the first-stage planet gears 324. The ringgear 332 includes radially interior teeth that engage the teeth of thefirst-stage planet gears 324. As such, first-stage planet gears 324extend between, and engage with, the first-stage sun gear 322 and thering gear 332. In some embodiments, a ring gear cover 333 may be mountedwithin the interior of the ring gear 332. The ring gear cover 333functions to at least partially enclose the gear set 320 within the gearhousing 311.

As shown, the ring gear 332 is fixedly arranged within the interior ofthe rotatable gear housing 311, which as noted above is positioned onbearings 312 to rotate relative to the stationary housing element orspindle 351. With respect to the planetary gear set 320, the rotatablegear housing 311 and/or ring gear 332 may function as the power transferelement 133 relative to the engine 120. Additional details regarding thering gear 332 are provided below. The ring gear 332 and/or rotatablegear housing 311 may be considered output and/or input elements of thepower transmission assembly 132 to receive rotational input in bothpower flow directions. Additionally, the ring gear 332 and/or rotatablegear housing 311 may be considered part of the mounting arrangement 305of the power transmission assembly 132 with respect to the engine 120,as discussed in greater detail below.

The gear set 320 further includes a second-stage sun gear 334 that isgenerally hollow and cylindrical, extending between first and secondends and circumscribing the input shaft 310. The first-stage planetcarrier 326 has a splined engagement with, or is otherwise fixed to, thesecond-stage sun gear 334 proximate to the second end. Additionally, thesecond-stage sun gear 334 may include a series of splines that mesh witha set of second-stage planet gears 340. The second-stage planet gears340 are supported by a second-stage planet carrier 342 formed by firstand second planet carrier plates. The second-stage planet gears 334 arepositioned to additionally engage with the ring gear 332. Thesecond-stage planet gears 334 each have an axle that extends between thetwo carrier plates that enable each planet gear 340 to rotate relativeto the planet carrier 342 about the respective axle. As such, thesecond-stage planet gears 340 are positioned in between, and engage witheach of, the second-stage sun gear 334 and the ring gear 332. Eachsecond-stage planet gear 334 has the same or a different number of teethrelative to a corresponding first-stage planet gear 324.

As introduced above, the clutch arrangement 350 of the powertransmission assembly 132 configured to selectively engage and disengagewith various components of the planetary gear set 320 to modify thepower flow according to the modes noted above. The cam actuationapparatus 390 operates to actuate the clutch arrangement 350. The viewof FIG. 8 additionally depicts the axial flange 398 that facilitatesmounting the reaction member 392 of the cam actuation apparatus 390 toenable interaction between the cam actuation apparatus 390 and theclutch arrangement 350, and thus, between the clutch arrangement 350 andthe gear set 320. Actuation mechanisms other than those depicted ordescribed may be provided.

In the view of FIG. 8, the low clutch 360 is in the disengaged positionand configured to be actuated by the solenoid devices 410, 430 via thelinkage assemblies 412, 432 and actuation pins 416, 436. As noted above,the low clutch 360 may be mounted on a stationary spindle 351 (or otherstationary housing element).

Although not shown in the cross-sectional view of FIG. 8, the solenoiddevices 410, 430 may be engaged to pivot the link members of linkageassemblies 412, 432 about the pivot members on the first face 393 of thereaction member 392 such that the actuation pins 416, 436 axiallyreposition the low clutch 360 into the gear set 320. In this example,the solenoid devices 410, 430 are energized for engagement. Uponengagement with the gear set 320, the low clutch 360 is configured tolock the second-stage planet carrier 342 to a stationary housing elementsuch as spindle 351, i.e., to ground the second-stage planet carrier 342and prevent rotation. With the low clutch 360 in the engaged positionand the mid and high clutches 370, 380 maintained in the disengagedpositions, the power transfer assembly 132 is configured to operate inthe cold engine start mode.

In the cold engine start mode, the engine 120 may be initially inactive,and activation of the ignition by an operator in the cabin 108 of thework vehicle 100 energizes the electric machine 134 to operate as amotor. In particular and additionally referring to FIG. 3, the electricmachine 134 rotates the pulley 220 in the first clock direction D1,thereby driving the belt 230 and pulley 210 in the first clock directionD1. The pulley 210 drives the input shaft 310, in the first clockdirection D1. Rotation of the input shaft 310 drives rotation of thefirst-stage sun gear 322, and in turn, rotation of the first-stage sungear 322 drives rotation of the first-stage planet gears 324. Thefirst-stage planet gears 324 drive the first-stage planet carrier 326,which as noted above is splined with the second-stage sun gear 334. As aresult, the first-stage planet carrier 326 drives the second-stage sungear 334 and thus the second-stage planet gears 340. As noted above, thesecond-stage planet carrier 342 is grounded by the low clutch 360. Assuch, rotation of the second-stage planet gears 340 operates to drivethe ring gear 332. Since the number of second-stage planet gears 340 inthe power flow path is an odd number (e.g., 1), the second-stage planetgears 340 drive the ring gear 332 in the opposite direction (e.g., thesecond clock direction D2) relative to the second-stage sun gear 334rotating in the first clock direction D1. As noted above, the ring gear332 functions as part of the power transfer element 133 to interfacewith the drive plate 309 mounted to the engine 120 to drive andfacilitate engine start. In effect, during the cold engine start mode,the power transmission assembly 132 operates as a sun-in, ring-outconfiguration.

In one example, the power transmission assembly 132 provides a 15:1 gearratio in the power flow direction of the cold engine start mode. Inother embodiments, other gear ratios (e.g., 10:1-30:1) may be provided.Considering a 4:1 gear ratio from the power transfer belt arrangement200, a resulting 60:1 gear ratio (e.g., approximately 40:1 to about120:1) may be achieved for the starter-generator device 130 between theelectric machine 134 and the engine 120 during the cold engine startmode. As such, if for example the electric machine 134 is rotating at10,000 RPM, the drive plate 309 mounted to the engine 120 rotates atabout 100-150 RPM. In one example, the power transmission assembly 132may deliver a torque of approximately 3000 Nm to the engine 120.Accordingly, the electric machine 134 may thus have normal operatingspeeds with relatively lower speed and higher torque output for coldengine start up.

In order to transition into another mode, the solenoid devices 410, 430are disengaged (e.g., de-energized, in this example) and the low clutch360 may be moved back into the disengaged position. This may beimplemented in a number of ways. In one example, a spring (not shown) ismay be provided on the second side 362 of the low clutch 360 such that,upon removal of the force from the solenoid devices 410, 430, the springbiases the low clutch 360 back into the disengaged position. Othermechanisms may be provided.

Although not shown in FIG. 8, the solenoid devices 450, 470 may beengaged to pivot the link members of the linkage assemblies 452, 472about the pivot members on the first face 393 of the reaction member 392such that the actuation pins 456, 476 axially reposition the mid clutch370 into the gear set 320. In this example, the solenoid devices 450,470 are energized for engagement. Upon engagement of the mid clutch 370,the first-stage planet carrier 326 is locked to the stationary housingportion such as spindle 351, i.e., to ground the first-stage planetcarrier 326 and prevent rotation.

When the mid clutch 370 is engaged and the low and high clutches 360,380 are disengaged, the power transmission assembly 132 is configured tooperate in the warm engine start mode. In the warm engine start mode,the engine 120 may be initially inactive or active. In any event, thecontroller 150 energizes the electric machine 134 to operate as a motor.In particular and additionally referring to FIG. 3, the electric machine134 rotates the pulley 220 in the first clock direction D1, therebydriving the belt 230 and pulley 210 in the first clock direction D1. Thepulley 210 drives the input shaft 310, in the first clock direction D1.Since the first-stage sun gear 322 is mounted on the input shaft 310,rotation of the input shaft 310 also rotates the first-stage sun gear322. In turn, rotation of the first-stage sun gear 322 drives rotationof the first-stage planet gears 324. Since the first-stage planetcarrier 326 and second-stage sun gear 334 are grounded, rotation of thefirst-stage planet gears 324 drives rotation of the ring gear 332. Sincethe number of first-stage planet gears 324 in the power flow path is anodd number (e.g., 1), the first-stage planet gears 324 drive the ringgear 332 in the opposite direction (e.g., the second clock direction D2)relative to the input shaft 310 and the first-stage sun gear 322rotating in the first clock direction D1. As noted above, the ring gear332 functions as the power transfer element 133 to interface with thedrive plate 309 mounted to the engine 120 to drive and facilitate enginestart. In effect, during the warm engine start mode, the powertransmission assembly 132 operates as a sun-in, ring-out configuration,albeit at a lower gear ratio as compared to the cold engine start mode.

In one example, the power transmission assembly 132 provides a 4:1 gearratio in the power flow direction of the warm engine start mode. Inother embodiments, other gear ratios (e.g., 3:1-7:1) may be provided.Considering a 4:1 gear ratio from the power transfer belt arrangement200, a resulting 16:1 gear ratio (e.g., approximately 12:1 to about28:1) may be achieved for the starter-generator device 130 between theelectric machine 134 and the engine 120 during the warm engine startmode. As such, if for example the electric machine 134 is rotating at10,000 RPM, the drive plate 309 mounted to the engine 120 rotates atabout 600-700 RPM. In one example, the torque output of the powertransmission assembly 132 for the engine 120 is approximately 400-600Nm. Accordingly, the electric machine 134 may thus have normal operatingspeeds with a relatively lower speed and higher torque output for enginestart up.

In order to transition into another mode, the solenoid devices 450, 470are disengaged (de-energized, in this example) and the mid clutch 370may be moved back into the disengaged position. This may be implementedin a number of ways. In one example, a spring (not shown) is may beprovided on the second side of the mid clutch 370 such that, uponremoval of the force from the solenoid devices 450, 470, the springbiases the mid clutch 370 back into the disengaged position. Othermechanisms may be provided.

Although not shown in FIG. 8, the solenoid devices 490, 510, 530 may beengaged to pivot the link members of linkage assemblies 492, 512, 532about the pivot members on the first face 393 of the reaction member 392such that the actuation pins 496, 516, 536 axially reposition the highclutch 380 into the gear set 320. In this example, the solenoid devices490, 510, 530 are energized for disengagement and de-energized forengagement. As such, to transition into the disengaged position, currentto the solenoid devices 490, 510, 530 may be discontinued and a springwithin the solenoid devices 490, 510, 530, on the high clutch 380, or onthe sliding hub 388 may urge the into the engaged position. Uponengagement of the high clutch 380, sliding hub 388 engages to lock theinput shaft 310 and the ring gear cover 333 to rotate together.

With the high clutch 380 in the engaged position and low and mid clutch360, 370 in disengaged positions, the power transmission assembly 132 isconfigured to operate in the boost mode or generation mode. In order totransition into another mode, the solenoid devices 490, 510, 530 aredisengaged (e.g., energized, in this example) and the high clutch 380may be moved back into the disengaged position.

In the boost mode, the engine 120 is active and the electric machine 134operates as a motor. In particular and additionally referring to FIG. 3,the electric machine 134 rotates the pulley 220 in the first clockdirection D1, thereby driving the belt 230 and pulley 210 in the firstclock direction D1. The pulley 210 drives the element 135, and thus theinput shaft 310, in the first clock direction D1. Rotation of the inputshaft 310 drives rotation of the first-stage sun gear 322, and in turn,rotation of the first-stage sun gear 322 drives rotation of thefirst-stage planet gears 324.

As noted above, the input shaft 310 is locked to the ring gear 332 bythe high clutch 380 when engaged. As a result, rotation of the inputshaft 310 drives the ring gear 332, as well as of the first-stage sungear 322, the first-stage planet gears 324, the first-stage planetcarrier 326, the second-stage sun gear 334, and the second-stage planetgears 340, about the primary rotational axis 300. In effect, the gearset 320 rotates as a unit about the primary rotational axis 300. Sincethe other components of the planetary gear set 320 rotate with the inputshaft 310, the ring gear 332 is driven in the same second clockdirection D2. As noted above, the ring gear 332 functions as part of thepower transfer element 133 to interface with the drive plate 309 mountedto the engine 120 to drive the engine 120. In effect, during the boostmode, the power transmission assembly 132 operates as a sun-in, ring-outconfiguration.

In one example, the power transmission assembly 132 provides a 1:1 gearratio in the power flow direction of the boost mode. In otherembodiments, other gear ratios may be provided. Considering a 4:1 gearratio from the power transfer belt arrangement 200, a resulting 4:1 gearratio may be achieved for the starter-generator device 130 between theelectric machine 134 and the engine 120 during the boost mode. As such,if for example the electric machine 134 is rotating at 10,000 RPM, thedrive plate 309 mounted to the engine 120 rotates at about 2500 RPM.Accordingly, the electric machine 134 may thus have normal operatingspeeds while providing an appropriate boost speed to the engine 120.

The power transmission assembly 132 has the same configuration toprovide a generation mode as in the boost mode. However, in thegeneration mode, the engine 120 drive the power transmission assembly132 and thus the electric machine 134.

For the generation mode (and subsequent to the engine start modes and/orthe boost mode), the engine 120 begins to accelerate above rotationalspeed provided by power transmission assembly 132, and the electricmachine 134 is commanded to decelerate and to cease providing torque topower transmission assembly 132. After the engine 120 has stabilized toa sufficient speed and the electric machine 134 has sufficientlydecelerated or stopped, the high clutch 380 is engaged as describedabove to operate the power transmission assembly 132 in the generationmode.

In the generation mode, the engine 120 rotates the drive plate 309engaged with the ring gear 332, thus driving the ring gear 332 in thesecond clock direction D2. The ring gear 332 drives the first-stageplanet gears 324 and the second-stage planet gears 340, whichrespectively drive the first-stage sun gear 322 and the second-stage sungear 334, and further driving input shaft 310. Therefore, as the ringgear 332 rotates in the second clock direction D2, the input shaft 310is driven and similarly rotates in the second clock direction D2 at thesame rate of rotation. As noted above, the input shaft 310 is connectedwith and provides output power to the electric machine 134 in the secondclock direction D2 via the power transfer belt arrangement 200. Ineffect, during the generation mode, the power transmission assembly 132operates as a ring-in, sun-out configuration.

In one example, the power transmission assembly 132 provides a 1:1 gearratio in the power flow direction of the generation mode. In otherembodiments, other gear ratios may be provided. Considering a 4:1 gearratio from the power transfer belt arrangement 200, a resulting 4:1 gearratio may be achieved for the starter-generator device 130 between theelectric machine 134 and the engine 120 during the generation mode. As aresult, the electric machine 134 may thus have normal operating speedsin both power flow directions with relatively low torque output duringpower generation.

Additional details regarding the interaction of the power transmissionassembly 132 and the engine 120 will now be provided. In particular, thepower transmission assembly 132 includes the mounting arrangement 305that supports and rotationally couples the power transmission assembly132 to the engine 120.

Referring again to FIG. 8 and as introduced above, the ring gear 332 isintegral with the cylindrical rotatable gear housing 311. The ring gear332 includes a number of castellations 540 that extend radially into aflex plate 550 that is mounted to a drive plate 309. The drive plate 309is mounted to the crank shaft of the engine 120 (FIG. 3). A closer viewof the engagement of a ring gear castellation 540 with the flex plate550 mounted on the drive plate 309 is provided by the view of FIG. 9. Ineffect, this arrangement 305 provides a direct coupling (e.g., withoutbolts) between the engine 120 (FIG. 3) and the power transmissionassembly 132.

Reference is briefly made to FIG. 10, which is an isometric engine-sideview of the power transmission assembly 132 with the drive plate 309removed. As introduced above, the mounting arrangement 305 includes aset of leg members 306 extending from the stationary housing portion303. The leg members 306 are sized and shaped such that the drive plate309 (not shown in FIG. 10) mounted to the flex plate 550 may engage withthe engine crank shaft. The distal ends of the leg members 306 may besecured to the engine 120 with bolts or other fasteners (not shown). Ineffect, the leg members 306 function to provide stationary support andas a reaction member for to the power transmission assembly 132 relativeto the engine 120.

The views of FIGS. 11 and 12 are isometric views of the ring gear 332and the flex plate 550. As best shown in FIG. 12, the ring gear 332 isan integral (one-piece) member with an inner surface 541, an outersurface 542, a first (electric machine-side) perimeter surface 543, anda second (engine-side) perimeter surface 544. As introduced above,splines 545 are formed in the inner surface 541 to order to engage withthe first-stage planet gears 324 and the second-stage planet gears 340.The castellations 540 extend in a radial direction about thecircumference of the second perimeter surface 544. In one example, thering gear 332 has six castellations 540, although other examples mayhave different numbers of castellations 540.

The flex plate 550 may also be formed by an integral member in oneexample. As shown, the flex plate 550 is generally ring-shaped with aninner perimeter 551 and an outer perimeter 552. The flex plate 550includes a circumferential row of engagement apertures 553 configured toreceive the castellations 540 of the ring gear 332 when assembled. Theengagement apertures 553 are sized and shaped to accommodate thecastellations 540 in order to secure the castellations 540 in thecircumferential direction, while enabling relatively easy radial andaxial access during mounting and dismounting of the power transmissionassembly 132 relative to the engine 120.

The flex plate 550 further includes a circumferential row of mountingholes 554. In this example, the mounting holes 554 are radially interiorto the engagement apertures 553. As described below, the mounting holes554 are utilized the mount the flex plate 550 to the drive plate 309.

The flex plate 550 may have a slight bend or slant in the radialdirection towards the ring gear 332 from the inner perimeter 551 to theouter perimeter 552 (or a slight bend or slant in the radial directionaway from the ring gear 332 from the outer perimeter 552 to the innerperimeter 551). The provides a radial resiliency to the flex plate 550that accommodates some amount of relative radial movement between thepower transmission assembly 132 and the engine 120. The resiliency ofthe flex plate 550 may be turned to balance insertion load relative totorsional application loads. The flex plate 550 may also provide ananti-rattle and/or anti-noise function for the power transmissionassembly 132.

Reference is now made to FIG. 13, which is an exploded isometric view ofthe flex plate 550 and the drive plate 309. As introduced above, theflex plate 550 includes a series of mounting holes 554 configured toreceive fasteners 555 to secure the flex plate 550 to the drive plate309.

In this example, the drive plate 309 is a torsional damper. As such, thetorsional damper 309 functions dampen vibrations at the crank shaft ofthe engine 120. The torsional damper 309 may utilize fluid or springs todissipate vibrations from the crank shaft of the engine and/or the ringgear 332. In some examples, the drive plate 309 may be a separateelement from the torsional damper.

As also shown in FIG. 13, the drive plate 309 includes a series ofmounting holes 556 to receive the fasteners 555 and secure the flexplate 550 to the drive plate 309. Accordingly (and additionallyreferring to FIGS. 14 and 15), in order to couple the ring gear 332 tothe drive plate 309, the flex plate 550 is initially secured to thedrive plate 309 with the fasteners 555. The castellations 540 of thering gear 332 are then inserted into the engagement apertures 553 of theflex plate 550. Subsequently, the drive plate 309 is mounted to thecrank shaft of the engine 120 (FIG. 3) and the mounting leg members 306(FIG. 10) are also secured to the engine 120 (FIG. 3). In this manner,the ring gear 332 of the transmission assembly 132 may be rotationallycoupled to the engine 120 for torque transfer without requiring a boltor other type of fastener for the ring gear 332.

Thus, various embodiments of the vehicle electric system have beendescribed that include an integrated starter-generator device. Varioustransmission assemblies may be included in the device, thus reducing thespace occupied by the system. The transmission assembly may providemultiple speeds or gear ratios and transition between speeds/gearratios. One or more clutch arrangements may be used to selectively applytorque to the gear set of the transmission assembly in both power flowdirections. Direct mechanical engagement with the engine shaft reducesthe complexity and improves reliability of the system. Using planetarygear sets in the transmission assembly provides high gear reduction andtorque capabilities with reduced backlash in a compact space envelope.As a result of the bi-directional nature of the power transmissionassembly, the power transfer belt arrangement may be implemented withonly a single belt tensioner, thereby providing a relatively compact andsimple assembly. Additionally, by using the power transfer beltarrangement with belt and pullies to couple together and transfer powerbetween the electric machine and the power transmission assembly,instead of directly connecting and coupling the electric machine to thepower transmission assembly, the electric machine may be mounted apartfrom the transmission assembly to better fit the engine in a vehicleengine bay. Additionally, by using the belt and pullies to couple theelectric machine to the power transmission assembly, an additional gearratio (e.g., a 4:1 ratio) may be achieved. Embodiments discussed aboveinclude a double planetary gear set, sun in, ring out configuration toprovide warm and cold engine start modes and a ring in, sun outconfiguration to provide a generation mode. As such, a four-modeassembly may be provided. The embodiments above further enable themounting of the power transmission assembly without the use of bolts orfasteners in order to simplify and improve assembly and performance.Additionally, the mounting arrangement between the power transmissionassembly and the engine may be implemented with torsional dampers and/oranti-rattle features to improve operation.

Also, the following examples are provided, which are numbered for easierreference.

1. A combination starter-generator device for a work vehicle having anengine, the starter-generator device comprising: an electric machine; agear set configured to receive rotational input from the electricmachine and from the engine and to couple the electric machine and theengine in a first power flow direction and a second power flowdirection, the gear set configured to operate in one of at least a firstgear ratio, a second gear ratio, or a third gear ratio in the firstpower flow direction and at least a fourth gear ratio in the secondpower flow direction, wherein the gear set includes a ring gear formedby a cylindrical base with a perimeter surface facing the engine and acircumferential row of castellations extending in a radial directionfrom the perimeter surface; and a mounting arrangement comprising adrive plate configured to be secured to a crank shaft of the engine anda flex plate mounted to the drive plate, wherein the flex plate includesa row of engagement apertures configured to receive the castellations ofthe ring gear to rotationally couple the ring gear to the engine via themounting arrangement.

2. The combination starter-generator device of example 1, wherein themounting arrangement further comprises a primary housing that at leastpartially encloses the gear set and at least one mounting leg extendingfrom the primary housing for mounting the combination starter-generatordevice to the engine.

3. The combination starter-generator device of example 2, wherein the atleast one mounting leg includes three mounting legs.

4. The combination starter-generator device of example 2, wherein thedrive plate includes a torsional damper configured to dampen vibrations.

5. The combination starter-generator device of example 4, wherein thecylindrical base and castellations of the ring gear are integrallyformed.

6. The combination starter-generator device of example 5, wherein thecastellations of the ring gear and the engagement apertures of the flexplate enable circumferential engagement between the ring gear and theflex plate without the ring gear being fixedly secured to the flex platein a radial direction.

7. The combination starter-generator device of example 1, furthercomprising a belt and pulley coupled to the gear set and the electricmachine, wherein input power in the first power flow direction isconveyed from the electric machine to the gear set by the belt andpulley, and wherein in the first power flow direction the belt andpulley rotate in the first clock direction and in the second power flowdirection the belt and pulley rotate in the second clock direction.

8. The combination starter-generator device of example 7, furthercomprising a single belt tensioner applying tension to a first side ofthe belt in both the first power flow direction and the second powerflow direction.

9. The combination starter-generator device of example 8, wherein thegear set comprises a compound epicyclic gear train including the ringgear, an input shaft, first-stage and second-stage sun gears,first-stage and second-stage planet gears, and first-stage andsecond-stage carriers with the first-stage planet carrier splined to thesecond-stage sun gear, wherein rotational power from the electricmachine moves in the first power flow direction from the sun gear to thering gear to the engine, and wherein rotational power from the enginemoves in the second power flow direction from the ring gear to the sungear to the electric machine.

10. The combination starter-generator device of example 9, furthercomprising: at least one clutch selectively coupled to the gear set toeffect the first, second, and third gear ratios in the first power flowdirection and the fourth gear ratio in the second power flow direction;and an actuation assembly including at least one electromechanicalsolenoid device configured to selectively shift the at least one clutchfrom a disengaged position in which the at least one clutch is decoupledfrom the gear set into an engaged position in which the at least oneclutch is coupled to the gear set.

11. The combination starter-generator device of example 10, wherein theat least one clutch includes at least a first clutch, a second clutch,and a third clutch, each configured as a dog clutch to selectivelyengage the gear set.

12. The combination starter-generator device of example 11, wherein, ina cold engine start mode, the first clutch is in the engaged position toground the second-stage planet carrier and the second and third clutchesare in the disengaged positions, and further, rotational power from theelectric machine moves in the first power flow direction from the inputshaft, to the first-stage sun gear, to the first stage-planet gears, tothe first-stage planet carrier, to the second-stage sun gear, to thesecond-stage planet gears, and to the ring gear out to the engine at thefirst gear ratio; and wherein, in a warm engine start mode, the secondclutch is in the engaged position to ground the first-stage planetcarrier and the first and third clutches are in the disengagedpositions, and further, the rotational power from the electric machinemoves in the first power flow direction from the input shaft, to thefirst-stage sun gear, to the first stage-planet gears, and to the ringgear out to the engine at the second gear ratio.

13. The combination starter-generator device of example 12, wherein, ina boost mode, the third clutch is in the engaged position to couple theinput shaft to the ring gear and the first and second clutches are inthe disengaged positions, and further, the rotational power from theelectric machine moves in the first power flow direction from the inputshaft, to the first-stage and second-stage sun gears, to the first-stageand second-stage planet gears, and to the ring gear out to the engine atthe third gear ratio; and wherein, in a generation mode, the thirdclutch is in the engaged position to couple the input shaft to the ringgear and the first and second clutches are in the disengaged positions,and further, rotational power from the engine moves in the second powerflow direction from the ring gear, to the first-stage and second-stageplanet gears, to the first-stage and second-stage sun gears, and to theinput shaft out to the electric machine at the fourth gear ratio.

14. The combination starter-generator device of example 13, wherein eachof the third gear ratio and the fourth gear ratio is a 1:1 ratio throughthe gear set, and wherein the first gear ratio is greater than thesecond gear ratio, and the second gear ratio is greater than the thirdgear ratio.

15. A drivetrain assembly for a work vehicle, comprising: an engine; anelectric machine; a gear set configured to receive rotational input fromthe electric machine and from the engine and to couple the electricmachine and the engine in a first power flow direction and a secondpower flow direction, the gear set configured to operate in one of atleast a first gear ratio, a second gear ratio, or a third gear ratio inthe first power flow direction and at least the third gear ratio in thesecond power flow direction, wherein the gear set includes a ring gearformed by a cylindrical base with a perimeter surface facing the engineand a circumferential row of castellations extending in a radialdirection from the perimeter surface; at least one clutch selectivelycoupled to the gear set to effect the first, second, and third gearratios in the first power flow direction and the fourth gear ratio inthe second power flow direction; an actuation assembly configured toselectively shift the at least one clutch from a disengaged position inwhich the at least one clutch is decoupled from the gear set into anengaged position in which the at least one clutch is coupled to the gearset; and a mounting arrangement comprising a drive plate configured tobe secured to a crank shaft of the engine and a flex plate mounted tothe drive plate, wherein the flex plate includes a row of engagementapertures configured to receive the castellations of the ring gear torotationally couple the ring gear to the engine via the mountingarrangement.

As will be appreciated by one skilled in the art, certain aspects of thedisclosed subject matter can be embodied as a method, system (e.g., awork vehicle control system included in a work vehicle), or computerprogram product. Accordingly, certain embodiments can be implementedentirely as hardware, entirely as software (including firmware, residentsoftware, micro-code, etc.) or as a combination of software and hardware(and other) aspects. Furthermore, certain embodiments can take the formof a computer program product on a computer-usable storage medium havingcomputer-usable program code embodied in the medium.

Any suitable computer usable or computer readable medium can beutilized. The computer usable medium can be a computer readable signalmedium or a computer readable storage medium. A computer-usable, orcomputer-readable, storage medium (including a storage device associatedwith a computing device or client electronic device) can be, forexample, but is not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, ordevice, or any suitable combination of the foregoing. More specificexamples (a non-exhaustive list) of the computer-readable medium wouldinclude the following: an electrical connection having one or morewires, a portable computer diskette, a hard disk, a random-access memory(RAM), a read-only memory (ROM), an erasable programmable read-onlymemory (EPROM or Flash memory), an optical fiber, a portable compactdisc read-only memory (CD-ROM), an optical storage device. In thecontext of this document, a computer-usable, or computer-readable,storage medium can be any tangible medium that can contain, or store aprogram for use by or in connection with the instruction executionsystem, apparatus, or device.

A computer readable signal medium can include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal can takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium can be non-transitory and can be anycomputer readable medium that is not a computer readable storage mediumand that can communicate, propagate, or transport a program for use byor in connection with an instruction execution system, apparatus, ordevice.

Aspects of certain embodiments are described herein can be describedwith reference to flowchart illustrations and/or block diagrams ofmethods, apparatus (systems) and computer program products according toembodiments of the disclosure. It will be understood that each block ofany such flowchart illustrations and/or block diagrams, and combinationsof blocks in such flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions can be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions can also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions can also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide steps for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

Any flowchart and block diagrams in the figures, or similar discussionabove, can illustrate the architecture, functionality, and operation ofpossible implementations of systems, methods and computer programproducts according to various embodiments of the present disclosure. Inthis regard, each block in the flowchart or block diagrams can representa module, segment, or portion of code, which includes one or moreexecutable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block (or otherwisedescribed herein) can occur out of the order noted in the figures. Forexample, two blocks shown in succession (or two operations described insuccession) can, in fact, be executed substantially concurrently, or theblocks (or operations) can sometimes be executed in the reverse order,depending upon the functionality involved. It will also be noted thateach block of any block diagram and/or flowchart illustration, andcombinations of blocks in any block diagrams and/or flowchartillustrations, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The description of the present disclosure has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. Explicitly referenced embodiments herein were chosen anddescribed in order to best explain the principles of the disclosure andtheir practical application, and to enable others of ordinary skill inthe art to understand the disclosure and recognize many alternatives,modifications, and variations on the described example(s). Accordingly,various embodiments and implementations other than those explicitlydescribed are within the scope of the following claims.

What is claimed is:
 1. A combination starter-generator device for a workvehicle having an engine, the starter-generator device comprising: anelectric machine; a gear set configured to receive rotational input fromthe electric machine and from the engine and to couple the electricmachine and the engine in a first power flow direction and a secondpower flow direction, the gear set configured to operate in one of atleast a first gear ratio, a second gear ratio, or a third gear ratio inthe first power flow direction and at least a fourth gear ratio in thesecond power flow direction, wherein the gear set includes a ring gearformed by a cylindrical base with a perimeter surface facing the engineand a circumferential row of castellations extending in a radialdirection from the perimeter surface; and a mounting arrangementcomprising a drive plate configured to be secured to a crank shaft ofthe engine and a flex plate mounted to the drive plate, wherein the flexplate includes a row of engagement apertures configured to receive thecastellations of the ring gear to rotationally couple the ring gear tothe engine via the mounting arrangement.
 2. The combinationstarter-generator device of claim 1, wherein the mounting arrangementfurther comprises a primary housing that at least partially encloses thegear set and at least one mounting leg extending from the primaryhousing for mounting the combination starter-generator device to theengine.
 3. The combination starter-generator device of claim 2, whereinthe at least one mounting leg includes three mounting legs.
 4. Thecombination starter-generator device of claim 2, wherein the drive plateincludes a torsional damper configured to dampen vibrations.
 5. Thecombination starter-generator device of claim 4, wherein the cylindricalbase and castellations of the ring gear are integrally formed.
 6. Thecombination starter-generator device of claim 5, wherein thecastellations of the ring gear and the engagement apertures of the flexplate enable circumferential engagement between the ring gear and theflex plate without the ring gear being fixedly secured to the flex platein a radial direction.
 7. The combination starter-generator device ofclaim 1, further comprising a belt and pulley coupled to the gear setand the electric machine, wherein input power in the first power flowdirection is conveyed from the electric machine to the gear set by thebelt and pulley, and wherein in the first power flow direction the beltand pulley rotate in the first clock direction and in the second powerflow direction the belt and pulley rotate in the second clock direction.8. The combination starter-generator device of claim 7, furthercomprising a single belt tensioner applying tension to a first side ofthe belt in both the first power flow direction and the second powerflow direction.
 9. The combination starter-generator device of claim 8,wherein the gear set comprises a compound epicyclic gear train includingthe ring gear, an input shaft, first-stage and second-stage sun gears,first-stage and second-stage planet gears, and first-stage andsecond-stage carriers with the first-stage planet carrier splined to thesecond-stage sun gear, wherein rotational power from the electricmachine moves in the first power flow direction from the sun gear to thering gear to the engine, and wherein rotational power from the enginemoves in the second power flow direction from the ring gear to the sungear to the electric machine.
 10. The combination starter-generatordevice of claim 9, further comprising: at least one clutch selectivelycoupled to the gear set to effect the first, second, and third gearratios in the first power flow direction and the fourth gear ratio inthe second power flow direction; and an actuation assembly including atleast one electromechanical solenoid device configured to selectivelyshift the at least one clutch from a disengaged position in which the atleast one clutch is decoupled from the gear set into an engaged positionin which the at least one clutch is coupled to the gear set.
 11. Thecombination starter-generator device of claim 10, wherein the at leastone clutch includes at least a first clutch, a second clutch, and athird clutch, each configured as a dog clutch to selectively engage thegear set.
 12. The combination starter-generator device of claim 11,wherein, in a cold engine start mode, the first clutch is in the engagedposition to ground the second-stage planet carrier and the second andthird clutches are in the disengaged positions, and further, rotationalpower from the electric machine moves in the first power flow directionfrom the input shaft, to the first-stage sun gear, to the firststage-planet gears, to the first-stage planet carrier, to thesecond-stage sun gear, to the second-stage planet gears, and to the ringgear out to the engine at the first gear ratio; and wherein, in a warmengine start mode, the second clutch is in the engaged position toground the first-stage planet carrier and the first and third clutchesare in the disengaged positions, and further, the rotational power fromthe electric machine moves in the first power flow direction from theinput shaft, to the first-stage sun gear, to the first stage-planetgears, and to the ring gear out to the engine at the second gear ratio.13. The combination starter-generator device of claim 12, wherein, in aboost mode, the third clutch is in the engaged position to couple theinput shaft to the ring gear and the first and second clutches are inthe disengaged positions, and further, the rotational power from theelectric machine moves in the first power flow direction from the inputshaft, to the first-stage and second-stage sun gears, to the first-stageand second-stage planet gears, and to the ring gear out to the engine atthe third gear ratio; and wherein, in a generation mode, the thirdclutch is in the engaged position to couple the input shaft to the ringgear and the first and second clutches are in the disengaged positions,and further, rotational power from the engine moves in the second powerflow direction from the ring gear, to the first-stage and second-stageplanet gears, to the first-stage and second-stage sun gears, and to theinput shaft out to the electric machine at the fourth gear ratio. 14.The combination starter-generator device of claim 13, wherein each ofthe third gear ratio and the fourth gear ratio is a 1:1 ratio throughthe gear set, and wherein the first gear ratio is greater than thesecond gear ratio, and the second gear ratio is greater than the thirdgear ratio.
 15. A drivetrain assembly for a work vehicle, comprising: anengine; an electric machine; a gear set configured to receive rotationalinput from the electric machine and from the engine and to couple theelectric machine and the engine in a first power flow direction and asecond power flow direction, the gear set configured to operate in oneof at least a first gear ratio, a second gear ratio, or a third gearratio in the first power flow direction and at least the third gearratio in the second power flow direction, wherein the gear set includesa ring gear formed by a cylindrical base with a perimeter surface facingthe engine and a circumferential row of castellations extending in aradial direction from the perimeter surface; at least one clutchselectively coupled to the gear set to effect the first, second, andthird gear ratios in the first power flow direction and the fourth gearratio in the second power flow direction; an actuation assemblyconfigured to selectively shift the at least one clutch from adisengaged position in which the at least one clutch is decoupled fromthe gear set into an engaged position in which the at least one clutchis coupled to the gear set; and a mounting arrangement comprising adrive plate configured to be secured to a crank shaft of the engine anda flex plate mounted to the drive plate, wherein the flex plate includesa row of engagement apertures configured to receive the castellations ofthe ring gear to rotationally couple the ring gear to the engine via themounting arrangement.
 16. The drivetrain assembly of claim 15, whereinthe mounting arrangement further comprises a primary housing that atleast partially encloses the gear set and at least one mounting legextending from the primary housing for mounting the combinationstarter-generator device to the engine.
 17. The drivetrain assembly ofclaim 15, wherein the drive plate includes a torsional damper configuredto dampen vibrations.
 18. The drivetrain assembly of claim 15, whereinthe cylindrical base and castellations of the ring gear are integrallyformed.
 19. The drivetrain assembly of claim 15, wherein thecastellations of the ring gear and the engagement apertures of the flexplate enable circumferential engagement between the ring gear and theflex plate without the ring gear being fixedly secured to the flex platein a radial direction.
 20. The drivetrain assembly of claim 15, furthercomprising: a belt and pulley coupled to the gear set and the electricmachine, wherein input power in the first power flow direction isconveyed from the electric machine to the gear set by the belt andpulley, wherein in the first power flow direction the belt and pulleyrotate in the first clock direction and in the second power flowdirection the belt and pulley rotate in the second clock direction; anda single belt tensioner applying tension to a first side of the belt inboth the first power flow direction and the second power flow direction.